Comparative Pharmacology
Head-to-head clinical analysis: LEVORA 0 15 30 21 versus NORTREL 0 5 35 28.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVORA 0 15 30 21 versus NORTREL 0 5 35 28.
LEVORA 0.15/30-21 vs NORTREL 0.5/35-28
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination oral contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; levonorgestrel inhibits ovulation and thickens cervical mucus, impairing sperm penetration. Also induces endometrial atrophy.
Norethindrone and ethinyl estradiol are a combination hormonal contraceptive. Norethindrone suppresses gonadotropin release (FSH and LH) from the pituitary, inhibiting ovulation. Ethinyl estradiol stabilizes the endometrium and enhances the contraceptive effect by inhibiting gonadotropin secretion.
One tablet orally once daily for 21 days, followed by 7 tablet-free days.
1 tablet orally once daily for 28 days (21 active tablets containing 0.5 mg norethindrone and 35 mcg ethinyl estradiol, followed by 7 placebo tablets).
None Documented
None Documented
20-30 hours for ethinyl estradiol; 2-4 hours for levonorgestrel. Steady-state reached in 5-7 days
Norethindrone: 7.2-9.2 hours; Ethinyl estradiol: 13-27 hours. Clinical context: Steady state reached in 5-7 days; half-life supports once-daily dosing.
Urine (50-60% as metabolites), feces (30-40% as glucuronides); <10% unchanged
Renal: ~40% as metabolites; Biliary/Fecal: ~60% as metabolites; <5% unchanged.
Category C
Category C
Oral Contraceptive
Oral Contraceptive